Lignin dispersing agents and method of making same

ABSTRACT

This invention relates to the production of dispersing agents from mixtures of spent sulphite liquor solids and Kraft liquor solids. Although appropriate physical mixtures of said solids without further treatment have useful dispersant characteristics for specific applications, the preferred way of preparing improved dispersant compositions from mixtures of said solids consists in heat treating concentrated aqueous solutions thereof for 1 to 3 hours at 100* to 160*C, at pH values higher than 11.0. The heat treatment is preferably performed under simultaneous blowing of air through the reaction mixture. The addition of a crosslinking agent, such as formaldehyde, is optional in cases where the air blowing treatment is not employed during the heat treatment. The dispersing agents of this invention have utility as dye dispersants, carbon black dispersants, clay dispersants, and the like.

nited States Patent [191 Benko et al.

[ LIGNIN DISPERSING AGENTS AND METHOD OF MAKING SAME [75] Inventors: Julius Benko, Sillery; Gilles Daneault, Sainte Foy, both of Quebec, Canada [73] Assignees Dryden Chemical Limited, Ontario,

Calif.

[22] Filed: Oct. 2, 1972 [21] Appl. No.: 293,898

[52] U.S. Cl 252/354, 8/83, 8/173, 252/313 R, 252/317, 252/353 [51] Int. Cl B0lf 17/50 [58] Field of Search 252/354, 353

[56] References Cited UNlTED STATES PATENTS 2,053,276 9/1936 Ellis 252/354 X 2,491,832 12/1949 Salvesen et al. 252/353 X 2,680,113 6/1954 Adler et al 260/124 2,933,452 4/1960 Byrd 252/353 3,153,564 10/1964 252/354 X 3,509,121 4/1970 Benko 260/212 X [451 Feb. 4, 1975 Primary Examiner-Richard D. Lovering Attorney, Agent, or Firm-Weir, Marshall, MacRae & Lamb [57] ABSTRACT This invention relates to the production of dispersing agents from mixtures of spent sulphite liquor solids and Kraft liquor solids. Although appropriate physical mixtures of said solids without further treatment have useful dispersant characteristics for specific applications, the preferred way of preparing improved dispersant compositions from mixtures of said solids consists in heat treating concentrated aqueous solutions thereof for 1 to 3 hours at 100 to 160C, at pH values higher than 1 1.0. The heat treatment is preferably performed under simultaneous blowing of air through the reaction mixture. The addition of a crosslinking agent, such as formaldehyde, is optional in cases where the air blowing treatment is not employed during the heat treatment. The dispersing agents of this invention have utility as dye dispersants, carbon black dispersants, clay dispersants, and the like.

8 Claims, No Drawings LIGNIN DISPERSING AGENTS AND METHOD OF MAKING SAME BACKGROUND OF THE INVENTION the spent sulphite liquor are based upon the dispersant I properties of lignosulphonates, its major component.

One of the first recorded uses of spent sulphite liquor solids in textile dyeing operations was described in German Pat. No. 222,191 of Mar. 5, 1909. At that time the requirements for dye dispersants were not severe and, thus, simple modifications and treatments of spent sulphite liquor were sufficient to produce dye dispersants acceptable for the then industrial practice. with the advancement of dyeing techniques in general, and the development of disperse dyes and dyeing techniques at high temperatures in particular, the requirements for acceptable dye dispersants have become more and more severe and, therefore, the successful ways of preparing them have become more and more elaborate.

The best dye dispersants prepared from spent sulphite liquor presently available have all been subjected to two different major treatments: namely, (1 a chemical treatment step to improve upon the dispersant properties of the lignosulphonate materials and (2) a physico-chemical treatment step consisting of fractionation for separating the dispersants from the nondispersant components of=the spent sulphite liquor. The sequence of the two steps may or may not be reversible depending upon the particular processing conditions.

A dye dispersant, particularly a disperse dye dispersant, has to have good or at least acceptable properties in the following:

. Grinding efficiency.

. Dye dispersant efficiency.

. Heat stability.

. Low staining characteristics.

. Good exhaustion characteristics.

Low viscosity in concentrated solutions.

Usually, none of the dye dispersants, whether prepared from spent sulphite liquors or from other raw materials, is capable of perfectly fulfilling all the above requirements. This implies that for specific applications, even within the same group of dyes such as dis- 7 Fractionation of the spent sulphite liquor products prior to or following any of the above chemical treatments is necessary. because the said reaction products are heterogeneous and the useful end-effect of some of their components becomes greatly diluted by the inert components of the mixture unless fractionation is performed. In addition to the undesired effect of dilution by inert components, harmful effects of the non-active ingredients of the chemically treated spent sulphite liquor have also occasionally been observed. For these reasons as well as the fact that in many dyestuff formulations there is no space for inactive ingredients. fractionation of the spent sulphite liquor products used for dye dispersants has become the general practice. The need for fractionation and one way of performing it have been described by J. Benko in US. Pat. No. 3,509,121 (Apr. 28, 1970).

Dispersant properties of the lignin material derived from the Kraft pulping process have also been known for a long time, although industrial utilization of dispersants prepared from Kraft lignins was much slower and is less common than the dispersant applications of lignosulphonates. The major difficulty in the successful application of Kraft lignins for a variety of dispersant applications is due to the fact that Kraft lignins do not form stable solutions or suspensions except in strongly alkaline media of pH 1 l or above, while most of the possible dispersant applications require a pH stability at much lower pH values. lt was due to this lack of solubility of-Kraft lignins at neutral and slightly acid pH values that sulphonation of Kraft lignins was introduced for making dispersant preparations therefrom. Significant improvements in this regard have been obtained through chemical treatments described by G. H. Thomlinson et al in US. Pat. No. 2,406,867 (Sept. 3, 1946) and by E. Adler et al. in US. Pat. No. 2,680,113 (July 1, 1954), and industrial utilization of Kraft lignins as dispersants, including dye dispersants, has ensued. In the production of dye dispersants from Kraft lignins the two basic steps are:

l. Fractionation of the Kraft lignins from Kraft liquor by means of acid precipitation, and

2. Sulphonation with or without crosslinking with formaldehyde.

The approaches to the utilization of the two major types of industrially available lignin materials, namely, lignosulphonates and Kraft lignins, for exacting dispersant applications, such as dye dispersant applications, have in common the need for fractionation of the lignin from the non-lignin materials, such as sugars, sugar acids and inorganic compounds. When comparing the chemical treatments, however, one observes that some of the chemical treatments of the lignosulphonate aim for the properties found in the Kraft lignins, namely: (lthe increase of the phenolic groups and 2) the reduction of sulphonic groups. On the other hand, some of the treatments of the Kraft lignins aim for an improvement of their end-use properties through (1 introduction of sulphonic groups, and (2) increase of molecular size, properties which are readily available in lignosulphonates.

SUMMARY OF THE INVENTION It has now been found that preparations from blends of spent sulphite liquors and Kraft liquors, according to the present invention, have unexpectedly advantageous dye dispersant properties. Lignosulphonates contained in the spent sulphite liquor and the alkali lignin contained in the Kraft liquor may be processed, according to the present invention, in such a way as to yield compositions that are (a) stable at neutral and moderatley acid pH values, (b) characterized by a suitable combination of dye dispersant properties having, among others, excellent grinding, dispersing and heat stability characteristics, and (c) further characterized by having acceptable, that is not excessively high, viscosities.

It is generally accepted in industrial practice that both the spent sulphite liquor solids and the Kraft liquor solids have to be fractionated, apart from being chemically treated in a variety of manners, in order to obtain dye dispersant preparations therefrom. All such fractionated preparations are characterized by a high lignin content, since part or all of the non-lignin components have been purposely removed. It was therefore surprising to find that dye dispersant properties equal to those obtainable according to the prior art may be obtained, for some applications, from a mixture of unfractionated spent sulphite liquor solids and unfractionated Kraft liquor solids treated according to the present invention. It was surprising to find that compositions of matter having 50 percent or less lignin content, with the balance of material consisting mostly of sugar acids and inorganic compounds, have for some applications dye dispersant properties equal to compositions prepared according to the prior art and consisting of fractionated and nearly pure lignin compositions from either spent sulphite liquor or Kraft lignins. Experimental evidence indicates that the improvements available through fractionation and a variety of chemical treatments are in several instances just about equal to the improvements available through purposeful combination and crosslinking of spent sulphite liquor and Kraft liquor solids, both being used without fractionation. Superior performance of mixtures, as compared to the performance of either one of its components alone, indicates a synergistic effect. The economic advantages of. using synergistic compositions and simultaneously avoiding fractionation and/or elaborate chemical treatments are obvious.

It has further been found that appropriate crosslinking of Kraft lignins with lignosulphonates by a variety of means may replace the otherwise necessary step of sulphonating Kraft lignin and yield improved dye dispersing agents stable at neutral and slightly acid pH values.

Hydrogen linkages are known to be important in aqueous solutions of spent sulphite liquors (LIGNINS, K. V. Sarkanen & C. H. Ludwig, Wiley-lnterscience, 1971, p. 750). It has been found that hydrogen linkages are readily established while mixing aqueous solutions of spent sulphite liquor solids and Kraft liquor solids at above pH 1 L at room temperature. After such mixing, the pH of said mixture may be lowered to neutral or even to a slightly acid pH without substantial precipitation of the Kraft lignin component therefrom. Apparently the linkage of Kraft lignins to lignosulphonates by means of hydrogen linkages prevents such precipitation. Such simple physical mixtures of Kraft liquors and spent sulphite liquors display dye dispersant properties sufficient for selected applications.

A further increase in the cross-linking between spent sulphite liquor solids and Kraft liquor solids yields compositions of matter characterized by improved dye dispersant characteristics and by improved low-pH stability. It is indicated by a variety of dye dispersant evaluation data that said increased crosslinkage, rather than the crosslinkage by means of hydrogen bonds alone, is

desirable for obtaining dye dispersant preparations for 5 general applicability. On the other hand, excessive crosslinking is to be avoided, since the resulting excessive viscosities are detrimental in the application of dye dispersants. The grinding of dyecakes with excessively viscous dye dispersants calls for greater than usual dilution which. in turn, diminishes the efficiency of the mill and which also reduces the efficiency in the subsequent drying operation. Crosslinking between the spent sulphite liquor solids and the Kraft liquor solids may be obtained by heating mixtures thereof with or without (a) the addition of formaldehyde or (b) oxidation by air blowing.

DESCRIPTION OF THE PREFERRED EMBODIMENT Dye dispersant compositions according to one embodiment of the present invention contain between about to 85 percent unfractionated spent sulphite liquor solids, with the balance ofthe material consisting of unfractionated Kraft liquor solids. Using less than about l5 percent spent sulphite liquor solids results in insufficient solubility of such compositions at lower pH values, while using less than about l5 percent Kraft liquor solids results in markedly diminishing improvements due to the insufficient addition of Kraft lignin material. Since both spent sulphite liquor solids and Kraft liquor solids are usually available in ample quantities and at low costs, there is no need to try to minimize the use of either one of these components and thus the preferred range of ingredients in the compositions is between 30 and 70 percent spent sulphite liquor solids with the balance being Kraft liquor solids. In another embodiment of the invention where fractionated materials are used, high molecular weight Kraft lignin is preferred for superior performance and such compositions may then contain between 10 and 75 percent of said high molecular weight Kraft lignin material with the balance being spent sulphite liquor solids.

The crosslinking betwen the spent sulphite liquor solids and the Kraft liquor solids can be obtained in the following ways:

1. By heat treating mixtures of liquors containing said solids between 100 and l60C for l to 3 hours, at pH values above 1 1.0 and at solids concentrations between and 50 percent.

2. By heat treating as in (l), with the addition of up to about 1 percent formaldehyde on the solids basis. 3. By heat treating as in (l), under simultaneous oxidation by means of air blowing.

The present invention is further described in the following Examples to V! with their associated Tables I to Vl, in which are assembled data from 45 experiments as a means of illustration and not of limitation.

The spent sulphite and the Kraft liquors used in the experiments were taken from industrial softwood pulping operations. The following notes further explain certain experimental conditions:

A. The spent sulphite liquor solids were preferably used in the sodium salt form.

B. For fractionation to obtain the high molecular weight lignins, the Kraft liquor was treated by acidification as described in the Thomlinson et al., patent and the Sarkanen 8L Ludwig text Lignins, both mentioned hereinbefore. The high molecular weight fractions of the spent sulphite liquor solids were prepared by the fractionation process described in the aforementhough a well qualified tester observes several additional properties of the dispersant in the course of the testing, such as efficiency ofgrinding, ease of rewetting and viscosity, only heat stability data are tabulated in tioned U.S. Pat. No. 3,509,121. 5 Tables I to V. This is done in order to present the data C. In order to maintain the pH of all preparations in an easy to understand manner, using the most imporabove ll.0 during the processing steps, the pH of the tant criterion only for the purpose of comparison. It is spent sulphite liquor solids in solution was raised to understood that good heat stability properties cannot over 13.0 prior to admixing with the Kraft liquor solube obtained under the standard experimental conditions. it was found that about lO percent by weight of It) tions if rewetting, grinding and dispersing properties as sodium hydroxide, calculated on the solids basis, was well as viscosity of the sample are not at least acceptrequired to be added to the spent sulphite liquor solids able. to be assured of a pH above 13.0. All spent sulphite liquor solids additions referred to in the Examples take EXAMPLE I into account such pH-adjusted solutions. Five different blends of Kraft lignin solids and spent D. The pH-adjusted spent sulphite liquor solids solusulphite liquor solids with three control samples of nontion may be first subjected to a heat treatment and he blended materials were heat treated under various reblended with the Kraft llqUOl SOlldS solution for further action conditions to provide dispersant compositions as heat treatment or it y be first blended with the Kraft set out in Table I. Table 1 indicates the limits of blendliquor SOlldS solution and then subjected 110 a heat treating ratios which resulted in useful compositions for dye ment, without any preliminary heat treatment. There dispersant applications. Experiments 4 and 5 show that appears to be no adherent advantage in the quality of blends having from about 10 to about 75 percent high the resulting compositions from either one operational molecular weight (HMW) Kraft lignins with the balprocedure or the other. ance being spent sulphite liquor solids produced re- E. The addition of small quantities of formaldehyde markably better dispersants than the non-blended ma- (up to about 1.0 percent on solids basis) during the terials of Experiments 1 to 3. heat treatment reaction results in improvement of rewetting properties and low pH stabilities. EXAMPLE ll F. Dye dispersant evaluation data are presented cusi wmarily on a comparative basis: that is the perform Seven different blends of unfractionated Kraft and ance of Sample preparations is compared with the Pep unfractlonated sulph te liquor solids were heat treated formance of an industrially accepted dye dispersant of under vanous co'idmons i dlspersam m excellent quality. The testing is performed as follows: Smons as Set out m Table i 9 to dye pastes are sand milled with the dispersant on a labcme that blended composmons f fmm P q oratory bench scale, under identical conditions, and Q to about 70 F unfrainmlmed hgm n5 the thus prepared dispersions are tested for dispersion f' the Palance be mg unfmctlonatFd spellt Sulpime and heat stability. The dispersion characteristics are liquor sollds are Suitable for dye dispersant applicatested by filtering the dispersion obtained by means of tlons' millin the d e-cake with the dispersant under standard condifions, a hd heat stability is established by means of 40 EXAMPLE several filter tests performed after different intervals of In addition to previous Experiments 4 and 5, Experisteam heating of the dispersions. The appearance f ments 16 to 20 are directed to heat treating, under variheavy residual matter indicates in the former case inous conditions, further blends of high molecular weight sufficient dispersion and, in the latter, the breaking of K ft lig i nd f ti d S m l hi li the dispersion due to excessive heat treatment. Allid as Set out i T bl l|[ TABLE I Limits of blending proportions for the production of efficient dyc dispersants within the scope of the present invention.

COMPOSITION REACTION CONDITIONS Dye dispersant evalua- Spent HCHO Solids tion on Dispcrsc Exp. Kraft Lignin Sulphite Li uor Added On Temperature Period Concentration Polyester Red: Heat No. Solids, Solids, z Solids Basis C hrs. w/v Stability (minutes) I none l00 1.] 140 1V2 51.0 9 min. (13 min.) 2 unfractionated, none [.4 I40 l V2 47.9 does not disperse I00 3 HMW, I00 none 0.8 I40 lVz 19.4 does not disperse 4 HMW, 25 0.5 I50 1 /2 29.0 17 min. (13 min.) 5 HMW; I0 1.0 l /z 4l.4 12 min. (13 min.) 6 unfraetionated, 85 0.67 140 l/: 49.l 8 min. (8 min.)

15 7 unfractionated, 15 0.67 140 1V2 50.2 11 min. (8 min.)

85 8 unfractionated, 8 0.67 M0 1 V2 48.5 does not disperse HMW High Molecular Weight NOTE: The heat stability data in buckets are the test results obtained on the same dyecake indicate a remarkable difference in the quality of the dyecakes for the first tin: and the last dye dispersant evaluation.

using a commercial dye dispersant of excellent quality. Results in Table l two tests, and emphasize the necessity for strict comparative testing in all TABLE II Dye dispersant preparations from unfractionated Kraft and unfractionated spent sulphlte liquor solids.

COMPOSITION REACTION CONDITIONS Dye dispersant evalua- Spent 74 HCHO Solids tion with Disperse Exp. Kraft Liquor Sulphite Liquor Added On Temperature Period Concentration Polyester Red: Heat No. Solids 7t Solids. 71 Solids Basis "C Hrs. w/v Stability (minutes) 9 30 70 1.3 140 W: 48.7 12 min. (13 min.) 10 5O 50 1.3 140 1V2 51.0 14 min.(13min.) ll 70 30 1.3 140 We 48.9 19 min. (13 min.) 12 30 70 none 140 l /z 51.4 8 min. (8 mini) 13 50 50 none 140 I 49.1 8 min. (8 min.) 14 7O 30 none 140 lbs 49.7 11 min. (8 min.) 15 70 30 05 I40 1 49.6 16 min. (8 min.)

NOTE: The heat stability data in brackets are the test results obtained on the same dyecake using a commercial dye dispersant of excellent quality. Results in Table II indicate a remarkable difference in the quality ofthe dyecakes used for the first three and the last four experiments and cm phasize the necessity for strict comparative testing in all dye dispersant evaluation.

TABLE III Dye dispersant preparations from HMW Kraft Liquor solids and unfractionated spent sulphite liquor solids.

COMPOSITION REACTION CONDITIONS Spent HCHO Solids Dye dispersant evalua- Exp. HMW Kraft Sulphite Li uor Added On Temperature Period Concentration tion with Disperse No Solids. Solids, Solids Basis C hrs. w/v Pol ester Red: Heat Sta ility (minutes) I0 90 I0 I40 /2 41.4 l2 min.(l3 min) 16 20 80 0.6 I40 1 41.7 14 min. (13 min) l7 90 none 150 2 50.3 13 min. (13 min I8 25 75 none 150 2 43.0 l4 min. (13 min I9 25 75 0.25 150 2 43.0 min. (13 min 2O 50 50 0.5 140 1% 27.3 17 min. (13 min.) 4 75 0.5 I 1% 29.0 l7 min. (13 min.)

NOTE; In addition. dye testing of the sample described in Exp. No.4 results in very good l0 minute heat stability on Disperse Red 17 and in fair heat stability on Disperse Red 60. The heat stability data in brackets are the test results obtained on the same dyecake. using a commercial dye dispersant of excellent quality.

TABLE IV Dye dispersant preparations from blends of HMW Kraft Iignin and HMW spent sulphite liquor solids.

Composition Percentages Reaction Conditions Dye Dispersant Evaluation HMW Solids On Disperse On Disperse On Disperse HMW Spent HCHO Concen- Polyester Red: Red No Red No 17: Exp. Kraft Sulphite Added On Temp. Period tration Heat Stability Heat Stability Heat Stability No. Lignin liquor Solids C. hours w/v (minutes) (5 min.steaming) (l0 min.steaming) solids Basis 21 7O 30 none none none 29.1 I I not tested not tested 22 30 none 1 15 1 29.1 I I not tested not tested 23 70 30 0.25 1 l5 1 29.1 I 1% not tested not tested 24 25 2.0 150 2 30.0 not tested fair-good good 25 50 50 1.0 150 2 31.2 not tested poor good 26 75 25 0.5 I50 1% 30.0 not tested good good 27 Commercial product of excellent quality 9 good good TABLE V The effect of air-blowing on dye dispersant preparations made from unfractionated Kraft liquor solids and unfractionated spent sulphite liquor solids.

Exp. Composition Reaction conditions Dye dispersant evalua- Nos. Kraft liquor Spent sul- Temp. Period. Solids Air tion on Disperse polysolids phite liquor C hours cone. blowing ester RedzHeat stabilsolids w/v ity (min) 28 70 30 I20 2 40 yes 8 29 70 30 I20 2 40 none poor rewctting 30 70 30 none none 40 none poor rewetting 31 70 30 3 41.3 yes 8% 32 70 30 I35 2 41.3 yes 8 33 70 30 none none 4L3 none poor rewetting 34 Commercial product of excellent quality 9 NOTE: In addition to improving the rewetting properties, air blowing also eliminates the characteristic odour of Kraft liquor.

Stability of dye dispersant preparations made from blends of Kraft liquor solids and spent sulphite liquor solids in weak acid medla.

Exp. Composition Reaction Conditions Volume precipitate from solutions No. of

Kraft liquor Spent sul- HCl-lO Temp. Period, solids 2.0% solids 0.5% solids solids, phite liquor added C. hours. conc.

solids, w/v. pH 5.0 pH 3.0 pH 5.0 pH 3.0

35 75 25 2.0 150 2 30 0.2 0.2 0.1 0.1 36 75 25 0.5 150 2 30 0.1 trace 20+ 37 70 30 none none none 29.1 3.0 20+ none 20+ 38 50 50 none 150 1 A 30 trace trace none none 39 50 50 0.8 150 1% 30 0.1 0.1 trace trace 40 50 50 none none none 30 trace 20+ trace 20+ 41 100 none none none 28.8 4.0 20+ trace 20+ 42 70 30 none 135 3 41.3 0.1 0.1 none trace 43 70 30 none 135 2 41.3 trace 12 none none 44 70 30 none 135 1 41.3 trace 20+ none none 45 70 30 none none none 41.3 trace 20+ none 20+ NONE: The extent of precipitation from solutions of 2.0% and 0.5% solids concentration was esiablished using a method originally devised for sludge determination in spent sulphite liquor solids. The sample is centrifuged at 3000 rpm. for 30 minutes and the volume percent of the precipitate is read EXAMPLE 1V Six different blends of fractionated Kraft and fractionated spent sulphite liquor solids were heat treated under various conditions to provide dispersant compositions as set out in Experiments 21 to 26 of Table IV. These compositions were favourably compared with a good commercial product (Experiment 27) in a heat stability dye dispersant evaluation test as shown in Table IV.

EXAMPLE V Six different blends of unfractionated Kraft and unfractionated spent sulphite liquor solids were heat treated under various conditions in Experiments 28 to 33 to show the effect of air blowing in the production of useful dispersants. These. compositions were then compared with a good commercial product (Experiment 34) to show that air blowing during the heat treatment process improves the dispersant properties of the blended compositions. The results are listed in Table V.

EXAMPLE Vl Three different compositions containing 50, 70 and 100 percent Kraft liquor solids and the remaining-percentages being spent sulphite liquor solids were heat treated under various conditions and the resulting compositions were then compared in Experiments 35 to 45 0 of Table V1 with compositlons obtained from similar blends of solids not subjected to heat treatment. Table VI enumerates the conditions of Experiments 35 to 45 directly from the calibration of the test tube w hich is calibrated up to 20% yolume and shows the stability of dilute solutions of certain dye dispersants in slightly acidic media of pHs 5.0 and 3.0.

The products of the present invention have utility as dispersants in applications other than as dye dispersants and in the following Example Vll there are described two further uses of these blends of spent sulphite liquor solids and Kraft lignins as carbon black and clay dispersants. The blend identified as CP 51 consisted of 67 percent Kraft lignins and 33 percent spent sulphite liquor solids, and was heat treated for 2 hours at 150C. with the addition of 0.5 percent formaldehyde on a solids weight basis.

EXAMPLE Vll A. Carbon Black Dispersion CP 51 was added in the form of a 10 percent aqueous solution to a 20 percent aqueous slurry of carbon black. The addition of 6.0 percent dispersant (weight/- weight basis) yielded a slurry having a viscosity of 66 cp. while the addition of 7.5 percent dispersant (w/w) yielded a slurry having a viscosity of 37.2 cp.

B. Clay Dispersion Data relating to the clay dispersant efficiency of CP 51 as compared with prior art dispersants. are shown in the following Table VI]. All measurements were made on 200 g aliquots of an 8.14 percent Wyoming hydrogel bentonite slurry in water. Following the addition of 1 ml quantities of 10 percent dispersant solution, the slurry was mixed for five minutes and viscosity readings were then taken on a Brookfield viscosimeter.

TABLE Vll Viscosity Changes in Centipoises following the Addition of Dispersant Solutions to Wyoming Hydrogel Bentonite Slurrics Addition in ml of 10% Sodium Salt Kraft Lignin Kraft Spent solution of Water Spent Sulphite Fractionated L' uor dispersant (control) CP 51 Liquor (acid precipitated) Unfractionated None 1700 17 1700 1700 1700 We claim:

I. A dispersant composition consisting essentially of a blend of Kraft liquor solids cross-linked with spent sulphite liquor solids, said solids being selected from the group consisting of the unfractionated liquor solids and the high molecular weight fractions thereof and said Kraft liquor solids comprising from about l percent to about 85 percent of said blend, on a solids weight basis, with said sulphite liquor solids comprising the remainder.

2. A composition as defined in claim I, wherein unfractionated Kraft liquor solids comprise from about 15 to about 85 percent of the blend, on a solids weight basis, and unfractionated spent sulphite liquor solids comprise the remainder.

3. A composition as defined in claim 1, wherein high molecular weight Kraft lignins comprise from about 10 to about 75 percent of the blend on a solids weight ba- SIS.

4. A dispersant composition consisting essentially of a blend of Kraft liquor solids cross-linked with spent sulphite liquor solids. said solids being selected from the group consisting of the unfractionated liquor solids and the high molecular weight fractions thereof and said Kraft liquor solids comprising from about 10 to about 85 percent of said blend. on a solids weight basis, with said sulphite liquor solids comprising the remainder, in the form of a concentrated aqueous solution.

5. A dispersant composition consisting essentially of a blend of Kraft liquor solids cross-linked with spent sulphite liquor solids, said solids being selected from the group consisting of the unfractionated liquor solids and the high molecular weight fractions thereof and said Kraft liquor solids comprising from about l0 to about percent of said blend, on a solids weight basis, with said sulphite liquor solids comprising the remainder. in the form of a spray dried powder.

6. A process for improving the dispersant properties of a blend of I) from about l0 to about 85 percent Kraft liquor solids, on a solids weight basis. and (2) spent sulphite liquor solids comprising the remainder. both said solids being selected from the group consisting of the unfractionated liquor solids and high molecular weight fractions thereof, which comprises subjecting said blend in a 25 to 50 percent w/v aqueous solution to heat treatment at a temperature in the range of about I 15C to C for from I to 3 hours.

7. The process defined in claim 6, wherein said heat treatment is carried out under simultaneous air blow- 8. The process defined in claim 6, wherein said solution additionally contains up to about 1.0 percent formaldehyde on a solids weight basis.

P0405) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,864,276 Dated August 6',- 197 Inventor(s) Jnlius Benko and Gilles Daneault It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below':

[- Title page, item [73] should read:- w

Dryden Chemicals Limited, Dryden, Ontario, Canada Signed and ficalc'cl this Twenty-third Day Of November 1976 [SEALI' Arrest:

RUTl-l C. MASON C. MARSHALL DANN ff Commissioner uflatems and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,864,276 Dated February 4, 1975 lnventofls) Julius Benko and Gilles Daneault It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title page, item [73] change "Calif," to Canada Signed and sealed this 29th day of April 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Comissioner of Patents Arresting Officer and Trademarks 

2. A composition as defined in claim 1, wherein unfractionated Kraft liquor solids comprise from about 15 to about 85 percent of the blend, on a solids weight basis, and unfractionated spent sulphite liquor solids comprise the remainder.
 3. A composition as defined in claim 1, wherein high molecular weight Kraft lignins comprise from about 10 to about 75 percent of the blend on a solids weight basis.
 4. A dispersant composition consisting essentially of a blend of Kraft liquor solids cross-linked with spent sulphite liquor solids, said solids being selected from the group consisting of the unfractionated liquor solids and the high molecular weight fractions thereof and said Kraft liquor solids comprising from about 10 to about 85 percent of said blend, on a solids weight basis, with said sulphite liquor solids comprising the remainder, in the form of a concentrated aqueous solution.
 5. A dispersant composition consisting essentially of a blend of Kraft liquor solids cross-linked with spent sulphite liquor solids, said solids being selected from the group consisting of the unfractionated liquor solids and the high molecular weight fractions thereof and said Kraft liquor solids comprising from about 10 to about 85 percent of said blend, on a solids weight basis, with said sulphite liquor solids comprising the remainder, in the form of a spray dried powder.
 6. A PROCESS FOR IMPROVING THE DISPERSANT PROPERTIES OF A BLEND OF (1) FROM ABOUT 10 TO ABOUT 85 PERCET KRAFT LIQUOR SOLIDS, ON A SOLIDS WEIGHT BASIS, AND (2) SPENT SULPHITE LIQUOR SOLIDS COMPRISING THE REMAINDER, BOTH SAID SOLIDS BEING SELECTED FROM THE GROUP CONSISTING OF THE UNFRACTIONED LIQUOR SOLIDS AND HIGH MOLECULAR WEIGHT FRACTIONS THEREOF, WHICH COMPRISES SUBJECTING SAID BLEND IN A 25 TO 50 PERCENT W/V AQUEOUS SOLUTION TO HEAT TREATMENT AT A TEMPERATURE IN THE RANGE OF ABOUT 115*C TO 160*C FOR FROM 1 TO 3 HOURS.
 7. The process defined in claim 6, wherein said heat treatment is carried out under simultaneous air blowing.
 8. The process defined in claim 6, wherein said solution additionally contains up to about 1.0 percent formaldehyde on a solids weight basis. 